In bi-directional ink jet printing systems, printing is accomplished by traversing a print head from side to side across a print medium while in both traversals droplets of ink are ejected from the print head onto the print medium to form an image. The quality of the printed image, which is built up from thousands of ink dots is affected by the characteristics of the individual dots. Ideally, the dots should be perfect circular spots of dried ink having a uniform size and each dot should be positioned on its corresponding pixel without extending into the neighboring pixels.
In practice, the array of dots is not perfect and deviation from the theoretical shape, size, and position of the dots may lead to defects in the printed image. Defects in the printed image may occur due to irregularity in the movement mechanism of the print head and/or medium, differences in the spacing between nozzles and differences in their size, wet ink expanding onto an area having another color (inter-color bleeding), and defects caused by the satellites of ink droplets.
The formation of the ink satellites lowers the quality of the printed image, in particular for wide-format ink-jet printing applications, in which the print head is moved at relatively high speeds. The high speed creates aerodynamic resistance forces that may split the ejected ink drop to create additional satellites. The formation of ink satellites may narrow the inter-color gap, which is a gap between two printed areas, and may blur the boundary between adjacent areas having different colors. It would be beneficial to reduce or eliminate banding artifacts and defects caused by satellite of ink droplets and ink drop dislocation.
Ink jet print heads having multiple nozzles or arrays of nozzles usually exhibit cross talk between the nozzles, which may affect the print quality. The operation of a large number of nozzles simultaneously for longer period of times during printing may reduce problems associated with the nozzles. The number of parallel operative nozzles depends, however, on the image content, namely the amount and position of printed areas. It would be beneficial to use a method of organizing and optimizing the image content data such that most of the nozzles operate simultaneously.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.